Black-pigmented members of the bacterial genus Bacteroides (BPB's) are colonists of the oral cavity, and are frequently found in association with oro-facial infections. Colonization of the oral cavity by these organisms must involve their adhesion to some component of the environment in order to resist being flushed away by saliva or the flow of crevicular fluid. Almost all strains of BPB's examined to date carry fimbriae: polymers of a protein subunit (fimbrilin) which form filaments that project from the cell surface. Considerable evidence has been accumulated from other bacterial species to show that fimbriae mediate specific adherence to a variety of surfaces such as epithelial cells or other bacteria. We proposed to test this hypothesis by determining the adhesive properties of BPB fimbriae. Since the BPB's form a group of related species, the question arises as to the evolutionary relationship of their fimbriae. Thus, we wish to determine if the BPB fimbriae are ancestrally related. If so, do they perform a conserved function or different functions? If they are unrelated but perform similar functions, is this due to convergent evolution? Relatedness will be determined by comparison of the nucleotide sequences of the cloned genes encoding the fimbrial protein subunits. Completion of these studies will provide, at the molecular level, an understanding of the strategies used by BPB's for fimbrial mediated adhesions. Information will be gained on the evolutionary pathways leading to these strategies and their potential roles in colonization of the oral cavity.